Conventional rigid endoscopes are essentially constituted by a metal tube for gaining access to the object to be observed and an optical system disposed inside the tube and having a set of lenses at one end and an eyepiece at the other end. An object is observed by placing the eye against the eyepiece, thereby receiving an image as conveyed by the optical "collectors".
Some systems allow a TV camera to be fitted to the eyepiece, with the overall assembly then being relatively heavy and mechanically inconvenient. These are called rigid video-endoscopes.
Given that it is rare, in practice, for an observer or a camera to be optimally oriented relative to an object to be observed, it is necessary to be able to adjust the orientation of the image provided by the optical system relative to the observer or to the above-mentioned camera.
In general, such image rotation is obtained in the prior art merely by rotating the tube that gives access to the objects to be observed. However, this manual operation is very fiddly because of the large number of connecting optical and electrical cables which end up by becoming tangled.
The object can be viewed either directly or obliquely (in particular at 90.degree. or 60.degree.) relative to the optical axis of the endoscope, with oblique viewing normally being obtained by means of a mirror disposed at the distal end of the tube giving access to the above-mentioned object.
However, at present, different endoscopes are used depending on whether the object is to be viewed directly or obliquely (or laterally), thereby increasing cost. In addition, when viewing obliquely, the use of a mirror presents at least two drawbacks, of which the first is due to reflection both on the silvered surface of the mirror and on the glass supporting the silvered surface, thereby creating an optical effect of superposed images which hinders viewing, and the second drawback is due to the deposition of pollutants (in particular dust) which are difficult to remove by virtue of the difficulty of gaining access to the inside of the tube containing the mirror and the danger of damaging the support glass, in particular by abrading it, which would therefore further degrade viewing.
The object of the present invention is therefore to provide a rigid video-endoscope which is more suitable for practical requirements than previously known rigid video-endoscopes seeking to perform the same function. In particular, the present invention seeks to make it easy to orient the image of the object to be observed as provided by the optical system without any danger of tangling the various cables.
Another object of the present invention is to provide a rigid video-endoscope which can be used either for direct viewing or for oblique viewing, depending on requirements, thereby avoiding the need to use two different devices.